Drier



be applied in appar Patented Dec. 7, 192a ulNiTEo STA mar aims w.'ranx,

res

PATENT oFFIcE.

.ENTS/TO PBOCTOR &'SCHWARTZ, INCL, OF PHILADELPHIA, PENNSYLVANIA, A

' conronarron or .rnmisnvnnm.

Application med A ru 1,

This invention relates to improvements in driers. More particularly it relates to air driers for material in a finely divided state, such as pigments, chemicals and the'hke,

although it will be evident that it can be heatedair horizontally therethrough, passing it over the exposed material in the trays;

Apparatus of this general type has been in use for many years in various forms. Itis an object of the present invention to provide improvements in the direction of increasing the speed and perfecting-the uniformity of the evaporating effect. It is also an object to provide the desired high eificiency at a low figure for first cost and for operation,- and with great simplicity of elements and arrangement. It is a further object'to arrange for the automatic shifting of the controls by whichthe moisture absorbing quality of the airis maintained at desired de-. gree, thereby limiting the consumption of steam or other heating agent and varying it according'to the varying needs at different stages of the drying. It is another object to produce a uniformity of effect wherever the material may happen to be located in the various trays. This is a matter of considerable n'nportance because for satisfactory results 1t 1s necessary to run the machmery until the whole-of each batch is dried'to the required degree." If there be a quantity of the moist material whichdries more slowly about the region opposite the axis of the fan,

ment of the invention,

' andlis flowing'to. the fan.

as I have foundin certain machinery tested, or if the material which is sheltered from draft of air because it /is next the .edgeof the tray, remains moist longer than that in the middle, there is waste of power and a marked reduction inthe capacity of the whole apparatus measured in quantity of output per it of time. I

In the apparatus'illustrated in the accony.

panying drawings, which show one embod1-.

{objects can'be attained by the simple means 'of constructing an element 'producmg diss tributive retardation of the air which has passed the trays where the'drying is done trays of the stack.

I have found that the In practice I,

' nmn.

1921; semi No. 457,080.

have found that a reduction of 10 per cent or :enovrnnncn, nnonn rsnann, assrei'won, BY nnsnn ASSIGN- of the area of the passage, making a vacuum of about one inch of water 'res'sure in the space immediately adjoinin the rotating fan, as compared with the s ace where the drying function upon the material, that th difference in pressure is hardly observabl as between the central and the top or bottoni .Moreover' by setting this retarding element at a little distance from the edge of the stack of trays, for which in practice I find 4 to 6 inches suitable, the nearer edges of the trays are in the stiller portion of the air, sothat the drying .pro-

ceeds with uniformity in all parts of each tray, down from the surface to the bottom 'of each tray load, both at the middle and close to the edges thereof. The openings through the retarding element provide uniformpull on air, adjacent stack section,

notwithstanding that the pull of the fan itself on air from top to bottom is not at all uniform. This is because of the equalizing effect of the vacuum from top tobottom of the.

chamber constituted between it and the fan.

The inventionfmay be applied in various forms; and it is intended that the patent shall cover bysuitable expression in the appended claims, whatever features of'patentable novelty exist in the invention disclosed.

In the accompanying drawings: Figure 1 is a front elevation n a complete drier; and

Figure 2 is a side elevation 9f the same in section on the} line 2+2 of Figure 1. Referring to thedrawings, 10 i dicates the whole, comprising top, bottom and four I sides, of an enclosure which is illustratedas having an entrance opening 11 and a discharge opening 12 for air and containing a fan 13', driven by any suitable means such as a pulle for drawing air from the inlet 11 toward -thedischarge. opening 12. (In ractice these openings -will bemore or ess closed respective by. the pivoted shut ters 11' and J2. so that the greater part of\ section, of

the air moved by the fan is merely circulated within the enclosure. To this end the encl'osure is divided on a horizontal plane about midway of its height by a partition 14 which extendsfrom front to back through the middle but stops short of each side or end so that air driven by the fan can there pass from the upper to the lower section at one end and from the lower to the upper section at the other end thus circulating aroundthe horiz ontal artition 14:. In the middle portion of the mclosure above and below thepartitions, are racks 15 which may contain trays 16, some of which are shown in position, to hold the material which is to be dried. The

racks for holding these trays are open-work affairs permitting the air to pass freely through them although the passage is, of course, somew at obstructed by the upright portions of the rack, if the same is made of angle iron as illustrated, or by the side wall of every tray which is in position. In each end section is a}, coil-18 of steam piping in I any suitable arrangement for heating the circulating air and reheating it according to well known practice.v

A principal feature of the invention consists in the provision of the retarding plate 20. In the arrangement illustrated in thedrawing the fan is at one end in the uppersection and is arranged .to draw the .air. away from the stack'oftrays in that section. A partition is provided around the perimeter of'the fan to centralize the flow of air therethrough and to prevent any retrograde movement thereof-past the fan.

The retarding plate is a foraminous partition placed entirely across the upper section at a location between the ends of the trays and the fan, whereby the area of the assage is reduced a predetermined amount,

isfactory. Its function is to restrict the flow of airto the entrance side of the fan so that the volume of airpassing through the plate is less than the capacity of the fan.

By thus limiting the quantity of air entering the chamber 22, located between the plate and the fan an observable degree of vacuum is created therein, which causes the pressure of the air in this chamber-Io be less than the pressure of theair on the tray side of the 'the fan, a large portion of the air is deflected downward past the end of the horizontal or which ten per cent has been found satpartition 14 into the lowersection of the drier. There it comes into contact with a coil of steam pipes which heat it and thereby increase its moisture absorbing capacity /as it flows around them, after which it passes through the framework of the rack, and on over and between the loaded trays of the material placed thereon to be dried. It continues through the rack at the other end of the trays beyond which its course is again altered so .that it moves upward through another heated coil of pipes, which.

perform the same. function as the. coil first encountered, and then horizontally againalong through the top section between the ing is cycle of movement.

Inasmuch as the action of the drier is very rapid the air in its repeated circulation of the enclosure soon would diminish in dryingpower. This is readily avoided by the arrangement of the openings 11 and 12, which are so placedv that a proportion of the air approaching the upper stack is drawn from outside fresh air, and a proportion of the air which leaves the fan goes outside, instead'of continuing in circulation. The necessity for changing the air diminishes as the moisture of thematerial in the traysbecome less; and it is therefore possible to thebottom section, taking up moisture from trays to the retarding plate, thus complet- I arrange for. the openings 11 and 12 to be gradually closed'during a drying operation.

A clock 24. or other suitable mechanism, having a revolving drum 26 is provided for winding up cables 27 and 28 which are fastenedto the shutters 11' and 12 respectively, and which upon being"wound on the drum cause these shutters to gradually close the openings 11 and 12. The shutters may be adjusted from time to time b hand, or may be operated and controlle by clock work. On standard work, when rate of progress can be forecast, such a'clock may be started'atlthe start of the run and may be arranged, for example, so 'that ,there is a cam or other rate var ing device (not shown) whose rotation y the. clock icont-rols the position of the shutters, Assuming that the material has 50 per cent of moisture at the start, and it will be suitable treatment, the cam may be so designed that for the first hour the openings of the shutters will remain at whatever stage they were set by the operator, and that thereafter? the clockand cam graduallywill close the openings until, say attheend of the 6th hour, only 10 per cent of the original moisture being then-left, the shutters are then *closed "and the run is completed in another two hours with the shutters closed. During o eration the retardin plate acts as an. equa izer for the flow t rough the stack, the flow of the same air being unequal through the immediately; adjacent fan, It

n om) acts somewhat like a dam having a wasteway extending entirely. across a stream of water, in that it produces a body of air whichis moving uniformly to the plate, and which bears somewhat the same relationto the air which has passed the plate as the still water in a reservoir does to the stream which issues from it. It is not necessary that this equalized air move at a high rate of speed, but its speed will depend more or less on the degree to which the retarding element obstructs the passage. As that fraction of the air which is about topass. higher velocity, it is desirable to put the retarding plate at a little distance from the stack, leaving the space for which in practice 4 inches has been found suifioient, so that the nearer edge of each tray is within the zonev ofstiller air equally with other parts of the tray. Under these circumstances the drying proceeds. with uniformity in all parts of each tray. A slight difference of pressure is suflicient to produce this result.

Apparatus such as that described has been discovered by experiment to give an improvement in efiiciency, resultingin a considerable saving'of power, as measured in the amount of. steam consumed, in heating and in power, per pound of water evaporated. The marked improvement which it has shown over other types that I have known,

- proach toward the theoretically possible minimum of steam required per pound of water evaporated, I consider tobe due to the fact that the equalizin of the drying avoids the waste found in ct er apparatus, where the operation of machinery has to be 00 tinned long after some parts are dry, and to the fact that it can be-controlled so that only the amount of fresh air actuall needed to.

. prevent too great rise of humidlty is intro-'- the amount of heating I duced, thus saving in needed.

I claim:

. 1. A drying apparatus comprising in'combination a rectangular enclosure, having one end open for free in ess of a drying agent, adapted to contain, t roughout substantially A the whole of its cross-sectional area, moist materialeto be dried; means a proximately filling the outlet end or the enc osure, adapts ed to exert a direct suctionat substantia y all .lpartfs of the cross-sectionaldarea of the out et, or rawing a as eous a nt through the enclosure past the 31 35; m a terial; and means, interposed between the last through the plate acquires with a close apsaid passage 4 approximate uniformity deuce,

said means and the material and extendingthroughout the cross-sectional area of the enclosure, adapted to equalize the velocity of the drying agent throughout the said cross containers, means, approximately filling the outlet end of the enclosure, adapted to exert a direct suction at substantially all parts of the cross-sectional area of the outlet, for drawing a gaseous drying. agent through the enclosure;

and a retarding plate )equal an size tothe outlet of the enclosure inserted across the path of the drying agent, whereby \velocity is equalized in that portion of the agent which is'held back; the said plate being spaced at a distance from the suctionmeans and at a little distance in the direction of flow beyond said containers, sufficient for the containers ,to be outside of the zone of increased velocity of the agent which is about to pass through the plate.

3; A drying apparatus comprising incombination an enclosure havin passagetherein with one en open for free ingress of air; containers arranged substan tially' throughout the cross-sectional area of for holding material to be dried; a fan almost filling the outlet end of the passage line ofdraft of air extending t rough and tainers; and means interposed between, and

spaced at a distance from, containers, comprising a foraminous pate having impervious portions distributed ith across the passage, between a multiplicity of small openings, whereby the flow of airv stricted .to less tial' vacuum is created in the passage between it and the plate, said vacuum andplate causing equalization of draft of air through allparts of said plate.

Signed at Providence, county of Provijmcnomsw. PARK.

a rectangular adapted to exert direct suction at substantially all parts of *tional area of the passage, arranged with its the fan and the to the/fan is re- I than its capacity, and a parand State of Rhode Island, this, twenty-sixth'd'ay of March, 1921.

the cross-sec- 

